Stellar mass-, sSFR-, and size-metallicity gradient relation for the 45 star-forming central galaxies (left, middle, and right panels, respectively). In the upper panels, the relations were constructed by using only ${\mathrm{\nabla }}_{\text{(O/H)}}^{\mathrm{Mid}}$. The colors of solid symbols encode the type of profile that was best fit to the whole metallicity distribution, inner break (IB; teal triangles), outer break (OB; orange triangles), and doubly broken (DB; gray hexagons). In the lower panels are the same relations but constructed using ${\mathrm{\nabla }}_{\text{(O/H)}}^{\mathrm{TS}}$ (red circles). Observational data from Martin & Roy (1995), Ho et al. (2015), and SM18 (MUSE); Franchetto et al. (2021) (MaNGA+MUSE); Chen et al. (2023) (TYPHOON); Cardoso et al. (2025) (CALIFA); and MaNGA DR17 are also displayed in a similar fashion. The black dashed line indicates ∇_(O/H) = 0 for reference purposes only. The two main galaxies LG1-4469 and LG1-4337 of the LG analog are highlighted, as they are later analyzed in detail as case studies.